1. Field of the Invention
The present invention relates to surgical probes which provide direct visualization for the surgeon at the distal end of the probe, and more particularly to such probes used for laser surgery to treat conditions such as benign prostate hyperplasia (BPH).
2. Description of the Related Art
With the advances in direct visualization techniques involving flexible, small diameter optical scopes that can be placed in a catheter, a surgeon is able to view a region being treated at the end of the catheter directly with the scope. However, when a direct visualization catheter is placed into a crowded region of the body, such as a hollow vessel, or a region between two organs which normally press together, the view through the scope may be obscured by tissue pressing on the scope.
There has been significant work in the area of direct visualization scopes using balloons to clear blood from the region of the tip of the scope to improve visualization. See Okada, et al., Balloon Cystoscopy with Neodymium:YAG Laser, THE JOURNAL OF UROLOGY, Vol. 148, 285-288, August 1992; Fujisawa, et al., Obtain Article. However, these designs have met limited success because of the difficulty in controlling the amount of laser radiation delivered through the balloon, and of preventing the radiation or effects caused by the radiation such as heat of the surrounding tissue from damaging or rupturing the balloon.
Other balloon type catheters have been used without direct visualization for a variety of treatments, including esophageal treatments as described in Panjehpour, et al., Centering Balloon to Improve Esophageal Photodynamic Therapy, LASERS IN SURGERY AND MEDICINE, 12:631-638 (1992). See also U.S. Pat. No. 4,998,930, to Lundahl, entitled INTRACAVITY LASER PHOTOTHERAPY DEVICE.
The results of such prior art systems have been mixed. Thus, there is a need for a direct visualization surgical probe mechanism which overcomes the difficulties encountered in the prior art, and which is suitable for use with delivery of laser radiation in controlled dosages.
One procedure in particular where such a probe is important is the treatment of Benign Prostate Hyperplasia (BPH). Generally, there are several ways to treat BPH. One type of treatment is trans-urethral incision of the prostate (TUIP) wherein a trans-urethral surgical instrument is inserted into the urethra to position an incisor adjacent the prostate gland. Once in position, an incision is made in the prostate into swollen tissue and reduce the amount of pressure the swollen gland exerts on the urethra. Other treatments for BPH include the use of drugs, or microwave hyperthermia.
A prevalent treatment in use today is trans-urethral resection of the prostate (TURP) wherein typically electro-cautery is used to remove swollen prostate tissue. Although many TURP techniques have developed, one current technique utilizes a laser probe, inserted into the urethra to direct laser energy onto selected portions of the enlarged gland, thereby creating coagulation necrosis of the target tissue, with the destroyed tissue sloughing off over time in tiny particles. The dead tissue particles are then passed out through the urethra upon urination.
One device for performing TURP in such manner is the Intra-Sonix TULIP System, manufactured by Intra-Sonix, Inc. of Burlington, Massachusetts. The Intra-Sonix TULIP device features a trans-urethral probe which is equipped with a single use balloon which is expandable at the distal tip of the probe. The distal end of the probe is inserted into the urethra and positioned adjacent the prostate, using a miniaturized ultrasound transducer and ultrasound imaging system. Once in place, the sleeve is expanded by pressurized sterile water and laser energy from a continuous wave Nd:YAG laser (1064 nm) of about 40 w of power is directed in a "side firing" manner onto the prostate.
Use of the pressurized sleeve or "balloon" at the tip of the probe provides both compression of the tissue adjacent the probe tip and a nominally constant distance between the probe tip and the tissue. Compression of the tissue allows deeper penetration of the laser energy into the tissue. A constant distance between the probe tip and the tissue is desired to ensure predictable energy distribution into the tissue.
However, the TULIP system is somewhat limited to the one particular use, i.e., TURP, since the system is designed to be used with its protective sleeve in all applications. Also, the TULIP system is quite expensive, requiring not only a laser, but also complex ultrasonic positioning mechanisms.
Another product recently announced is the Trimedyne "Lateralase" (also known as the "Eurolase"), by Trimedyne Corporation of Irvine, California. This device utilizes a catheter with a laser fiber designed to laterally direct laser energy to the affected area. Again, the Lateralase is designed to be inserted into the urethra and, once positioned adjacent to the prostate, to direct laser energy to a selected area of the prostate gland. The Lateralase laser probe is positioned visually by means of an endoscope, having an axial eyepiece aligned along the same axis defined by the length of the trans-urethral probe. The endoscope provides the surgeon with the most accurate representation of the effects of the laser on the areas of the prostate to which it is directed. However, the view may be obscured by swollen tissue and the like in the urethra.
In addition, the endoscope requires optical fibers coincident with the probe tip to provide light and viewing channels to the eyepiece. With the axial eyepiece being in line with the rigid trans-urethral cannula, placement of these fibers in the cannula in conjunction with the optical fiber for transmitting laser energy further complicates the structure of the surgical instrument.
Further, when using a flexible sheath and an optical fiber which is rotatable in the transverse plane, as in the TULIP system, it is desirable to have energy directed from the probe tip at a constant distance to the gland tissue over the entire rotation path to ensure uniformity in the amount of energy reaching the selected area. To ensure such equidistant length, the optical fiber for the laser in the TULIP system is centered with respect to the circumference of the sheath. Even centering the fiber does not ensure equidistance when the fiber tip is extended significantly beyond the tip of the probe due to possible flexing of the balloon relative to the probe or slight sagging of the fiber tip.
Another consideration in TURP systems is the temperature of the operating site. In particular, the heat generated by the laser incident on the tissue can cause the tissue to char, making it difficult to control the amount of tissue destroyed. Thus, it is desirable to control the temperature at the operating site such that coagulation necrosis of the tissue occurs at a rate which can be controlled by the surgeon.
It is also desirable to provide a surgical instrument utilizing a distension element, such as a balloon, to compress the tissue adjacent the energy delivery point and to tamponade superficial bleeding from the surface of the tissue. It is further desirable to ensure the distance between the energy delivery point and the tissue is constant when the balloon is distended and where the energy delivery point is rotatable in the transverse plane. It is also advantageous to provide such an instrument wherein an endoscope is utilized to view the surgical area, thereby yielding the most accurate representation of the surgical area to the surgeon. It is also desirable to provide such an instrument wherein the temperature at the operating site can be accurately controlled. Further, containment of the irrigation/cooling fluid may be critically important for some regions of the body such as the brain or blood vessels.